Search results

The purpose of this paper is to investigate the behavior of embedded passives under changing temperature conditions. Influence of different temperature changes on the basic properties of embedded passives was analyzed. The main reason for these investigations was to determine functionality of passives for space application.

The investigations were based on the thin-film resistors made of Ni-P alloy, thick-film resistors made of carbon or carbon-silver inks, embedded capacitors made of FaradFlex materials and embedded inductor made in various configurations. Prepared samples were examined under the influence of a constant elevated temperature (100, 130 or 160°C) in a long period of time (minimum of 30 h), thermal cycles (from −40 to +85°C) or thermal shocks (from −40 to +105°C or from −40 to +125°C).

The achieved results revealed that resistance drift became bigger when the samples were treated at a higher constant temperature. At the same time, no significant difference in change in electrical properties for 50 and 100 Ω resistors was noticed. For all the tests, resistance change was below 2 per cent regardless of a value of the tested resistors. Conducted thermal shock studies indicate that thin-film resistors, coils and some thick-film resistors are characterized by minor variations in basic parameters. Some of the inks may show considerable resistance variations with temperature changes. Significant changes were also exhibited by embedded capacitors.

The knowledge about the behavior of the operating parameters of embedded components considering environmental conditions allow for development of more complex systems with integrated printed circuit boards.

The paper aims to get the knowledge about electrical properties, including noise, of modern polymer thick-film resistors (TFRs) in a wide range of temperature values, i.e. from 77 K up to room temperature. The sample resistors have been made of different combinations of resistive compositions, either ED7100 or MINICO (M2013, M2010), and conducting pastes (for contacts) Cu- or Au-based, deposited on FR-4 laminate.

The paper opted for an experimental study using either current noise index measurement in room temperature for large batch of samples or noise spectra measurement in temperature range 77-300 K for selected samples. Obtained noise maps, i.e. plots of power spectral density of voltage fluctuations vs frequency and temperature, have been used for evaluation of noise describing parameters like material noise intensity C and figure of merit K, for TFRs made of different combinations of resistive/conductive materials. Comparison of the parameters gives the information about the quality of the technology and matching the conductive/resistive materials.

Experiments confirmed that the main noise component is 1/f resistance noise. However, low-frequency noise spectroscopy revealed that also noise components of Lorentzian shape, associated with thermally activated noise sources exist. Their activation energies have been found to be of a few tenths of eV.

The noise intensity of polymer TFRs depends on technology process and/or contacts materials. The use of Au contacts leads to better noise properties of the resistors. The results of the studies might be helpful for further improvement of thick-film technology, especially for manufacturing low-noise, stable and reliable TFRs.

The paper includes indications for the materials selection for thick-film technology to manufacture low-noise, reliable and stable TFRs.

Experimental studies of electrical properties of polymer TFRs by means of noise spectra measurements in wide range of temperature is rare. They give fundamental knowledge about noise sources in the modern passive electronic components as well as practical indications of selection material for thick-film technology, to obtain high performance components and get technological advantage.

Possible application of mixed (thick/thin film) thermopiles to supply autonomous microsystems.

PdAg/AG or PdAg/TSG thermocouples were deposited onto a circular alumina or LTCC substrates. Their thermoelectric power, resistance as well as output electrical power were characterized vs temperature gradient and chosen parameters of thermopile fabrication process.

Semiconductors have high Seebeck coefficient, so investigated kind of thermopile has high output electrical power E_T. It achieves 50 mV per single junction for temperature difference of about 200°C.

The problem is very high resistivity of germanium alloys, even after burn‐in process. Therefore output electrical power P is seriously reduced. To improve thermocouples properties, optimization process is required. For example, thin film layers quality can be improved, semiconductive arms width can be increased or shorter arms can be used.

Application of mixed thick/thin film technology for fabrication of miniaturized thermoelectric generators.

To find properties of screen printed PZT (PbZr_0.53Ti_0.47O₃ with 6 per cent of PbO and 2 per cent of Pb₅Ge₃O₁₁) thick films layers on LTCC substrate.

The influence of PZT firing time and electrode materials on electrical characteristics and microstructure were examined. A scanning electron microscope (SEM) equipped with an energy‐dispersive X‐ray (EDS) analyser was used for the microstructural and compositional analysis.

Microstructural and compositional analyses have shown the diffusion of SiO₂ from LTCC into PZT layers and the diffusion of PbO in the opposite direction. SiO₂ presumably forms low permitivity lead based silicates in PZT layer. The new phase deteriorates the piezoelectric properties. The amount of diffused materials was dependent upon the electrode material and increased with increasing firing time. Better properties, i.e. higher remanent polarisation and dielectric constant were achieved for samples with PdAg electrodes and shorter firing time.

New information on electrical and microstructural properties of thick film PZT made on LTCC substrate.

This paper aims to discuss and urge further deliberation on possible strategies to help geriatric and special needs patients to receive dental care during the pandemic.

This paper contains literature review of published research articles related to past epidemics, COVID-19 and older persons.

Accurate prediction of adverse outcomes, detection of unidentified problems, improved estimation of residual life expectancy and appropriate use of geriatric interventions is required to understand the necessity of the treatment and effect of possible COVID-19 contraction during the treatment.

The authors reviewed the only published literature and collated the lessons learnt from past epidemics, as the natural history of the COVID-19 is not known.

Future dentists must be trained in crisis management to deal with pandemics more effectively. The dental fraternity should be equipped to provide some sort of “psychological counseling and reassurance” prior to dental care to vulnerable individuals with comorbidities and special needs.

There are very few published articles focused on unique dental care plans for geriatric and special needs patients.

This paper aims to focus on the fabrication and characterization of mixed thin-/thick-film thermoelectric microgenerators, based on magnetron sputtered constantan (copper–nickel alloy) and screen-printed silver. To improve the adhesion of the constantan layer to the applied substrates, the additional chromium sublayer was used. The aim of the study was to investigate the influence of chromium sublayer on the electrical and thermoelectric properties of such hybrid microgenerators.

Fabrication of such structures consisted of several steps – magnetron sputtering of the chromium and then constantan layer, exposing the first arms of thermocouples, applying the second arms by screen-printing technology and firing the prepared structures in a belt furnace. The structures were made both on Al₂O₃ (alumina) and low temperature co-fired ceramics (LTCC) substrates.

To the best of the authors’ knowledge, for the first time, laser ablation process was applied to fabricate the first arms of thermocouples from a layer of constantan only or constantan with a chromium sublayer. Geometric measurements have shown that the mapping of mask pattern by laser ablation technique is very accurate.

The determined Seebeck coefficient of the realized structures was about 40.4 µV/K. After firing the exemplary structures at 850°C peak temperature, Seebeck coefficient is increased to an average value of 51 µV/K.

The purpose of this study was to design, fabricate and test devices based on transformers integrated with low-temperature co-fired ceramic (LTCC) modules with isolation between primary and secondary windings at the level between 6 and 12 kV.

Insulating properties of the LTCC were examined. Dielectric strength and volume resistivity were determined for common LTCC tapes: 951 (DuPont), 41020, 41060 (ESL), A6M (Ferro) and SK47 (KEKO). According to the determined properties, three different devices were designed, fabricated and tested: a compact DC/DC converter, a galvanic separator for serial digital bus and a transformer for high-voltage generator.

Breakdown field intensity higher than 40 kV/mm was obtained for the test samples set, whereas the best breakdown field intensity of about 90 kV/mm was obtained for 951 tape. The materials 41020 and 951 exhibited the highest volume resistivity. Fabricated devices exhibited safe operation up to a potential difference of 10 kV, limited by minimum clearance. Long-term stability was assured by over 20 kV strength of inner dielectric.

This paper contains description of three devices made in the LTCC technology for application in systems with high-voltage isolation requirement, for example, for power or railway power networks.

The results show that LTCC is a suitable material for fabrication of high-voltage devices with integrated passives. Technology and properties of three examples of such devices are described, demonstrating the ability of the LTCC technology for application in reliable high-voltage devices and systems.

This paper aims to present systematic studies of a wide spectrum of geometrical and electrical properties of thick‐film and LTCC microresistors (with designed dimensions between 50 × 50 μm² and 800 × 200 μm²).

The geometrical parameters (average length, width and thickness, relations between designed and real dimensions, distribution of planar dimensions) are correlated with basic electrical properties of resistors (sheet resistance and its distribution, hot temperature coefficient of resistance and its distribution distribution) as well as long term thermal stability and durability of microresistors to short electrical pulses.

Fodel process gives better resolution than standard screen‐printing and leads to smaller dimensions than designed, smaller absolute error and better uniformity of planar sizes. Microresistors made in full Fodel process show much weaker dimensional effect and exhibit noticeably smaller distribution of basic electrical properties.

Presents systematic studies of a wide spectrum of geometrical and electrical properties of thick‐film and LTCC microresistors.

The paper focuses on design, fabrication and characterization of electromagnetic microgenerators with integrated rectifying circuits to convert AC output signal to DC one. The work includes research on simulation of voltage-rectifying circuits, including charge pump, realization of the experimental printed circuit board (PCB) with selected electronic circuits and the execution of the final structure with integrated rectifying circuit. Measurements were performed on these circuits.

Electromagnetic microgenerators include multipole permanent magnets secured on rotor three-phase brushless direct current (BLDC) motor and planar multilayer multiple coils. These were fabricated using low temperature co-fired ceramics (LTCC) technology. In our experiment, six rectifying circuits were simulated and tested with a structure consisting of eight layers of coils and with an outer diameter of 50 mm fabricated earlier.

The microgenerator with Graetz bridge generates higher output power than the modified charge pump at the same rotary speed. However, it is less stable for the distance change between the structure and the magnets than the modified charge pump, which has more constant output power in a wider range of load resistance.

The presented electronic rectifying circuits are novel for LTCC-based electromagnetic microgenerator application. The structure with integrated rectifying circuits allows generation of electrical output power larger than 100 mW at the rotor speed of about 8,000 rpm.

The purpose of this paper is to characterize electrical properties of nickel-phosphorus (Ni-P) thin-film resistors made on FR-4 laminate in a wide range of temperature (from −180 to 20°C).

The study was performed using resistors made of Ni-P foil with two different thicknesses (0.1 or 0.05 μm) and sheet resistances (100 or 250 Ω/sq), respectively. The resistance rectangular resistors had length and width from the range between 0.59 and 5.91 mm. The resistance versus temperature characteristics and their distribution as well as resistors ' durability to low-temperature thermal shocks were investigated.

The results showed almost linear temperature dependence of resistance with a negative temperature coefficient of resistance of about −95 ppm/°C for 250 Ω/sq layer and −55 ppm/°C for 100 Ω/sq layer. A very small dimensional effect was observed for sheet resistance as well as for R(T) characteristic. Thin-film resistors are also characterized by very high durability to low-temperature thermal shocks.

The results presented in this paper can be very useful for low-temperature applications of thin-film resistors made on printed circuit boards. They suggest possibility of wide applications of these components in a wide temperature range.